Device to suspend and string conductors on low, medium, high and extra high transmission lines

ABSTRACT

Suspension device for the stringing of electric conductors and/or cables for overhead power lines, of the type comprising a suspension frame, to be anchored to a crossarm of a tower of the line, and means for the support and sliding of the conductors and/or cables, said support and sliding means comprising, for each conductor or cable, a plurality of support rollers rotating about parallel pins, said rollers being aligned one after the other along a curved trajectory and defining an ideal support and sliding surface for the conductor or cable. According to the invention, the support rollers for each conductor are divided in two groups forming two trajectory sectors; the two trajectory sectors supporting each conductor are mounted on the suspension frame in specular symmetry in respect of the central vertical suspension axis of said frame, said two trajectory sectors being mutually spaced; lifting and lowering means are moreover associated to said trajectory sectors, to move the trajectory sectors in a substantially vertical direction.

FIELD OF THE INVENTION

The invention relates to a suspension device that allows to support andstring conductors on low, medium, high, and extra high transmissionlines.

BACKGROUND OF THE INVENTION

It is well known to the experts in the art of power lines constructionthat the stringing and clamping-in procedures usually comprise thefollowing operations:

position one pulley per each crossarm of each tower and suspend each ofsaid pulleys from the strings of insulators hanging from each crossarm,

lay on the ground one service cable per each phase of the power lineaccording to the layout of the towers,

lift and position each service cable on each respective pulley,

tension each of said service cables from one end by means of a winch andfrom the other end by means of a brake,

pull the service cables by means of said winch, and replace each servicecable with a conductor and/or a larger draw cable if a bundle ofconductors has to be positioned per each phase of the line,

position all conductors and/or bundles of conductors on their respectivepulleys, while keeping said conductors and/or bundles of conductorsalways under tension and therefore always raised from the ground,

pull the conductors and/or bundles of conductors by means of said winchtill they reach the prescribed degree of tension (pre-sagging) (iflongitudinal unbalances are present the pre-sagging of the conductors atthis stage cannot be the equal to the final and correct sagging),

if longitudinal unbalances are present, due to the fact that the powerline is crossing mountains and/or the distance between towers is notconstant, calculate said longitudinal unbalances, and mark theplumb-point on each conductor so that once the conductors have beenclamped-in to said insulators, the insulators will be plumbed and theconductors sagged,

temporarily lift, by means of one or more tackles, the conductor and/oreach conductor of a bundle from the grooves of a pulley, remove saidpulley, clamp-in the conductor and/or conductors to the insulators, andonce all conductors have been clamped-in to the insulators of all towersbetween the brake and the winch, control, and often adjust, the saggingof said conductors.

It is to be understood that when longitudinal unbalances are present,before the crews can proceed with the last described operation, that isto say before they can clamp-in the conductors, said tackles have to beused not only to lift the conductors from the pulleys, but also to pullsaid conductors, with repeated operations, in order to recover thecalculated differences between the "rest" position of the conductors onthe pulley and the final clamp-in points. This additional operation hasto be carried out with absolute accuracy so that once said conductorshave been clamped-in to the insulators of all towers between the brakeand the winch, said insulators will remain perfectly plumbed, and onlyvertical loads will be imposed to the crossarms of suspension towers.

There are many difficulties related to the stringing of power lines andwhile some of them, particularly these relating to the positioning ofthe service cables on the towers, have been faced and solved for exampleas described in the U.S. Pat. No. 4,596,379 (Europe N.56285) of the sameassignee, patent that can be referred to for a better understanding ofstate of the art of the different stringing methodologies, the others,and particularly those relating to the clamping-in and plumbingoperations, have been faced, but not solved.

The difficulties relating to the clamping-in of the conductors to theinsulators, as partially explained, are the following:

1. stringing conductors on angle towers, that is to say on towers whichcause the conductors to run on different vertical planes, causes thepulleys to be displaced to a non-vertical position. The displacement ofthe pulleys, in its turn, causes the conductors to cross the grooves ofthe pulley. In fact, while the two catenaries adjacent to the tower arepoints. This additional operation has to be carried out with absoluteaccuracy so that once said conductors have been clamped-in to theinsulators of all towers between the brake and the winch, saidinsulators will remain perfectly plumbed, and only vertical loads willbe imposed to the crossarms of suspension towers.

There are many difficulties related to the stringing of power lines andwhile some of them, particularly those relating to the positioning ofthe service cables on the towers, have been faced and solved for exampleas described in the U.S. Pat. No. 4,596,379 (Europe N.56285) of the sameassignee (that patent that can be referred to for a better understandingof state of the art of the different stringing methods), the problemsrelating to the clamping-in of the conductors to the clamps of theinsulator chain, while keeping the conductors always under tension havebeen faced, but not solved.

The difficulties relating to the clamping-in of the conductors to theinsulators, as partially explained, are the following:

1. stringing conductors on angle towers, that is to say on towers whichcause the conductors to run on different vertical planes, causes thepulleys to be displaced to a non-vertical position. The displacement ofthe pulleys, in its turn, causes the conductors to cross the grooves ofthe pulley. In fact, while the two catenaries adjacent to the tower arecontained on perfectly vertical planes, the plane on which the pulleysheaves rotate is (in these cases) always sloped. Consequently, theconductors simultaneously touch the grooves of the pulley in points withdifferent peripheral speeds undergoing continuous abrasions and torsionswhich should not be allowed in order to preserve their integrity.

2. When longitudinal unbalances are not present, the points where theconductors rest in the grooves of the pulleys coincide with the pointswhere the suspension clamps have to be inserted for clamping-in.Consequently, said points of the conductors cannot be accessed by thecrews for clamping-in without first having to temporarily lift saidconductors and remove the pulleys.

3. When longitudinal unbalances are present, the clamping-in points donot coincide with the points where the conductors rest in the grooves ofsaid pulleys, but on the contrary they often are various meters awayfrom said rest-points. In these cases, the final sagging, clamping-in,and plumbing operations always require the processing of complicatedcalculations and the execution of difficult operations to be carried outexclusively on the towers in order to:

recover said longitudinal unbalances on line towers,

recover said longitudinal unbalances even on angle towers while forexample also compensating for the different lengths of the conductors ina bundle, and

clamp-in the conductors according to a specific geometric configuration.In addition to the complicated operations required to undo saidlongitudinal balances, these cases too always require to firsttemporarily lift the conductors from the pulleys, using numerous andsupplementary pieces of equipment, and then remove the pulleys beforeclamping-in.

4. The sagging, plumbing, and clamping-in operations briefly describedin point 3, can get to be so complicated that in the end, many times,they turn out to be mostly trial and error operations. Many times, afterthe conductors have been clamped-in to all towers, said conductors willstill be not perfectly sagged. In these cases the crews will have to goback from tower to tower and adjust the clamp-in points till saidconductors will be perfectly sagged and all insulators perfectlyplumbed.

In the Italian patent N.1191291, of the same assigned, the problems anddifficulties listed in points 1 and 2 had been dealt with through theuse of common pulley sheaves which had been mounted specularly on aspecial frame. Even though said pulley-units in theory partially solvedsome of the mentioned inconveniences and difficulties, they required theuse of many pulley sheaves having diameter at least equal to 80 cm.. Thenumber of pulley sheaves required was more than double the number ofconductors in a bundle, in fact for example in the described case of abundle of eight conductors the pulley-unit was composed by twenty pulleysheaves, sixteen of which had diameter equal to 80 cm.. The number ofpulley sheaves, their diameter, and the heavy structure of the frameadded up to an enormous increase of the weight, size, and manufacturingcosts of the whole unit. In addition, the weight and size of the unitalso created considerable difficulties to transport it to the towers andsuspend it from the insulators. Because of these reasons and othertechnical problems, the use of the pulley units described was completelyinefficient, uneconomic, and unjustifiable.

The present invention offers the best and most practical solution to thedifficulties listed in points from 1 to 4 and the technical andoperative/economic problems related to the pulley-units described in theItalian patent N.1191291. The present invention relates to: 1) thegeneral stringing method, because the clamping-in and sagging operationshave been substantially changed and; 2) the structure of the suspensiondevices that allow to string the service cables and/or conductors.

The new structure of the suspension devices, according to the presentinvention, allows: 1) the conductors and/or cables to freely run on saiddevices while stringing, 2) the insulators to be automatically andperfectly plumbed and the conductors to be automatically and perfectlysagged without the need of manual interventions and/or counterweights,and 3) the conductors to be directly clamped-in without the need ofeither lifting said conductors from their rest-position or usingtemporary and supplementary equipment. All being accomplished while atthe same time decreasing both the size and the weight of the suspensionunits. It is also to be noticed that the structure of the suspensionunits, according to the present invention, also allows to position allclamps necessary for the clamping-in operations within each suspensionunit further decreasing work time, and further simplifing the job to becarried out by the crews.

It is well known, that pulleys and/or pulley units commonly usedgenerally comprise: 1) a large suspension frame, to be suspended fromthe insulators often in correspondence of at least one of the holesdesigned for receiving the suspension clamps, in other words oftenoccupying at least one of the clamp-in points, and 2) one or more pulleysheaves.

The diameter of these pulley sheaves is usually very large, greater forexample than 60 cm. and often even greater than 100 cm.. in order toallow the conductors to run on said sheaves without bending too much.Because of the present trend of using conductors with larger diameters,the pulley sheaves are also tending to have larger diameters.

The just mentioned facts together with the tendency of using one bundleof conductors per each phase of the line, rather than one singleconductor, are the reasons why the commonly used pulleys have becomelarger and heavier. In fact, the commonly used pulleys, for example fora bundle of three conductors, weigh approximately 150-200 Kg., while thepulley unit for a bundle of eight conductors, described in the Italianpatent N.1191291, weighs approximately 1,500 Kg., and/or about 500 Kg.in the not described case of a unit for three conductors. The weight ofthe commonly used pulleys and/or pulley units described in said patentis not only an inconvenience from the manufacturing/cost point of view,but more than anything else from the point of view of their practicaluse on site. The pulleys and/or pulley units have to be transportedalong the power line, often in areas which cannot be reached by roadand/or cross country vehicles, lifted and suspended from the insulatorsfor stringing, and finally transported again to another tower. It isquite obvious that when a pulley and/or pulley unit weighs more than150-200 Kg. and/or more than 500-1,500 Kg. the transportation andlifting problems can become particularly burdensome.

As mentioned earlier, another serious problem related to the use of thecommon pulleys derives from the difficulty of clamping-in theconductors, both because of the reasons explained in points from 1 to 4,and because of the fact that often at least one of the clamp-in pointshas been occupied by the frame of the pulley. If using the commonpulleys for stringing is therefore necessary to first remove saidpulleys from their suspension point and then clamp-in the conductors.For these operations, to be repeated for each pulley of each tower, theprocedure is usually the following: first, temporarily lift theconductor and/or conductors, by means of one or more tackles and bringsaid conductor and/ or bundle of conductors in position to beclamped-in, secondly remove the pulley and bring it to the ground, andfinally clamp-in the conductor and/or bundle of conductors to theinsulators at the "right" points. These are very complicated operationsparticularly in consideration of the fact that the weight of eachconductor to be temporarily lifted can easily be greater than 1,000 Kg.and/or greater than 2,000 Kg.. As mentioned earlier, it is important tounderstand that when longitudinal unbalances are present the finalclamp-in points of each conductor never correspond with the rest-pointsof said conductors on the pulleys, but can get to be even more than 10m. away (down-hill) from said rest-points. In these cases the tacklesthat are applied on each conductor to lift them from the grooves of thepulleys, have to be attached to each conductor down-hill and far awayfrom the pulleys, in order to recover said various meters of conductorsthat cause the insulators to be out-of-plumb. This complicated operationalso implies to impose a longitudinal stress of thousands of kilogramsto each crossarm of many suspension towers, which are neither designednor manufactured to resist to said longitudinal stress, but only tovertical loads.

Suspension system of the type comprising a small frame and a pluralityof rollers disposed in continuous sequence as one sector of a crown,have been described in the U.S. Pat. No. 3,145,016 and in the Frenchpatents N.93165 and N.1104834. The primary objects of these patentswere: 1) for U.S. Pat. No. 3,145,016 to allow a sector of multiplepulley assemblage to automatically change the angle of load imposed onthe conductors in order not to damage said conductors while stringing,2) for the French patent N. 1104834 to reduce the weight and size of thesuspension units and 3) for the French patent N. 931675 to be able touse the same suspension unit for stringing any size conductors manuallychanging the position of the wheels so as to vary the angle of loadsimposed on different conductors. On the other hand, none of thesedevices was technically fitted to be practically used on site.

In addition, none of the listed patents allowed to either clamp-in theconductors directly (and at the right point) to the insulators withoutfirst having to remove the suspension units, or to string the conductorspassing through transversal angles without damaging the conductors.Moreover, none of the listed patents allowed to, automatically plumb theinsulators and perfectly sag the conductors, and automatically positiona bundle of conductors according to the prescribed geometricconfiguration, neither simultaneously on all towers between the brakeand the winch, nor with one or more operations without a directintervention of the crews on the conductors themselves.

SUMMARY OF THE INVENTION

The primary object of the present invention is to solve all the listedproblems and difficulties. In other words, the new suspension units,allow on one hand to maintain a reduced size and weight of the frames,and on the other hand: 1) to automatically plumb all insulators on alltowers between the brake and the winch, 2) to automatically andperfectly sag the conductors particularly if longitudinal unbalances arepresent, 3) to automatically position a bundle of conductors accordingto the prescribed geometric configuration, and 4) to clamp-in theconductors without having to temporarily lift the conductors from thesuspension units, and/or remove said suspension units.

These results are obtained with a device for the suspension andstringing of conductors and/or cables for overhead power lines , of thetype comprising a suspension frame, adapted to be suspended from acrossarm of a tower of the line, and means for the support and slidingof the conductors and/or cables, said support and sliding meanscomprising, for each conductor and/or cable, a plurality of supportrollers which, rotating about parallel pins, are aligned one after theother along a curved trajectory, said rollers defining an ideal supportand sliding surface for each respective conductor and/or cable. Thewhole suspensions device is essentially characterized by the fact that:

the support rollers for each conductor are divided in two groups ofrollers forming two trajectory sectors.

the two trajectory sectors comprising the support rollers for oneconductor are mounted on the suspension frame in specular symmetry inrespect of the central vertical axis of said suspension frame, said twotrajectory sectors being mutually spaced,

lifting and lowering means being also associated to the trajectorysectors, to move said trajectory sectors in a substantially verticaldirection.

BRIEF DESCRIPTION OF THE DRAWINGS

Other characteristics and advantages of the present invention will bemore readily understandable after the following detailed description ofsome of the preferred embodiments and ways to achieve the mentionedresults, illustrated, only as a way of example and not in limitativemanner, in FIGS. 1 to 20 where:

FIGS. 1 to 4 are schematic lateral views of different pairs oftrajectory sectors;

FIGS. 5 illustrates in more details one of the two trajectory sectorsillustrated in FIGS. 1 to 3;

FIG. 6 is a top view of the same trajectory sector;

FIG. 7 is a lateral section (VII--VII) of the trajectory sector in FIG.5;

FIG. 8 is an other lateral section (VIII--VIII) again of the sametrajectory sector;

FIG. 9 is a top view of a pair of trajectory sectors fitted to be usedon angle towers;

FIG. 10 is a lateral view of a trajectory sector fitted with onegeared-motor;

FIG. 11 is a partial section (XI--XI) of FIG. 10;

FIG. 12 is a lateral view of more pairs of trajectory sectors mounted onone special frame;

FIG. 13 is a front view of the suspension device illustrated in FIG. 12;

FIGS. 14 and 15 show a similar suspension device for stringing a bundleof these conductors on angle towers;

FIG. 16 is a top view illustrating the preferred dimensions and profilesof a series of rollers of one trajectory sector of the type illustratedin FIG. 4;

FIG. 17 is a schematic lateral view of the same trajectory sectorshowing the disposition of said rollers;

FIGS. 18 and 19 are two front views of the same trajectory sectorshowing the position of the rotation axis of said rollers;

FIG. 20 is a lateral view of the preferred type of suspension frame forstringing a bundle of three conductors on both line and angle towers.

DETAILED DESCRIPTION OF THE INVENTION

The first three possible variants, according to the present invention,of the device for the suspension of the cables and/or conductors areillustrated in FIGS. 1 to 3. In these three figures the device ismounted on a frame (1), and is substantially made up of two series ofrollers (2) and (2') which disposed, according to the first importantcharacteristic of the present invention, so as to form two separatetrajectory sectors (SS1) and (SS2), are spaced specularly from one another. It is to be noticed that by mounting more than one pair oftrajectory sector on each frame, the same frame can be used for thestringing and suspension of more than one cable and/or conductor (C).The top of frame (1) is connected to a special interface (A) which isrequired to hang said frame from the lower end of one or more strings ofinsulators.

More partricularly, FIG. 1 shows that the two trajectory sectors (SS1)and (SS2) are spaced from one another by means of two connecting bars(P2) (only one can be seen). The device, comprising the two trajectorysectors and the two bars (P2), is mounted on said frame (1) by means ofslides (4) that allow the parallel/vertical lifting and/or lowering ofthe trajectory sectors along the sides of frame (1). Once the conductor(C) has been clamped-in to the insulators (not shown), by inserting theclamp (not shown) in the central space between said trajectory sectors,the two trajectory sectors (SS1) and (SS2) can be unloaded of the weightof the conductor by acting on screws (5) which control said slides (4).Once the trajectory sectors (SS1) and (SS2) have reached the position(3") (illustrated with the dotted line), the whole suspension unit,including the frame, can be easily removed.

FIG. 2 shows an alternative to plates (P2) and slides (4) of FIG. 1. Inthis case, the two trajectory sectors (SS1) and (SS2) are spaced bymeans of four plates (P4) hinged to points (6a) and (6a') of frame (1).Once the conductor has been clamped-in, as explained for FIG. 1, the twotrajectory sectors are lowered to position (3"), again by acting onscrews (5), but this time thanks to their rotation about points (6a) and(7a'), rather than slides (4).

The last alternative for the spacing of said trajectory sectors (SS1)and (SS2) is illustrated in FIG. 3. Here, the two trajectory sectors arehinged to the base of frame (1) through a common pin (6b) and extensionarms (7). In this case the connecting plates (P2) and/or (P4) have beeneliminated, the frame is even smaller, but the central space between thetwo trajectory sectors (SS1) and (SS2) is not large enough to allow theinsertion of said clamp. Once the conductor has been suspended from aseries of towers, and is therefore lying on a series of trajectorysectors (SS1) and (SS2), before it can be clamped-in, said trajectorysectors have to be first moved to position (3'), by acting on screw(5a). At this point the suspension clamp can be inserted and theconductor clamped-in. Once the conductor has been clamped-in, trajectorysectors (SS1) and (SS2) are moved to position (3") by acting once againon said screw (5a). In this case thanks to screw (5a), which has adouble thread, and extension arms (7), the rotation of trajectorysectors (SS1) and (SS2) is eccentric.

FIG. 4 illustrates the preferred solution for the spacing lifting andlowering of two, also preferred, trajectory sectors. A pair oftrajectory sectors (SS3) and (SS4) are here spaced from one an other bymeans of one steel, or alloy channel section (P1) which is also used tostore at least one suspension clamp (not shown). The lifting and/orlowering of the two trajectory sectors together with element (P1) isneither achieved by slides (4) (FIG. 1), nor by the hinges illustratedin FIGS. 2 and/or 3, but by means of a bearing jack which is made up bytoggle arms (8), (8'), and (8"), and one or more lead screws (9).

Thanks to the solution of using at least one bearing jack, by acting onsaid one and/or more lead screws (9), the motion of said two trajectorysectors (SS3) and (SS4), together with element (P1), and/or more pair oftrajectory sectors of the same type, can either be: 1)parallel/vertical, for the positioning of a bundle of conductorsaccording to some prescribed geometric configuration and/or in order tounload said couples of trajectory sectors of the weight of eachconductor once said conductors have been clamped-in, and/or 2)oblique/vertical to either position said bundle of conductors accordingto other prescribed geometric configurations, and/or decrease thetendency of the strings of insulators to be displaced out-of-plumb whenlongitudinal unbalances are present.

FIG. 4 also shows that the two trajectory sectors (SS3) and (SS4) eachcomprise a series of rollers (R) and (R') which spaced as shown, havedifferent longitudinal dimensions and different profiles for the purposebetter described in FIGS. 16 to 19. The dimensions of element (P1) andtrajectory sectors (SS3) and (SS4) have been studied so as to allow theintroduction of at least one pair of jaws (G1) and (G2) and at least onegeared motor (MR1) and/or (MR2). At the right time, in a way betterdescribed later on, thanks to said geared motors, said pairs of jaws(G1) and (G2) in turn tighten and pull the conductor (C) for theautomatic plumbing of the insulators, and the respective automaticsagging of the conductor itself.

As explained earlier, in FIGS. 1 to 4 the position of the trajectorysectors (SS1) and (SS2), or (SS3) and (SS4) can be changed by acting onlead screws (5), or (5a), or (9). Those figures illustrated said leadscrews as if they could be hand-operated only, on the contrary, itshould be understood that said lead screws could also be automaticallyactived by means of at least one electric geared motor. FIGS. 5 to 8illustrate the details of trajectory sector (SS2) schematicallyillustrated in FIGS. 1 to 3. FIG. 7, which is section (VII--VII) of FIG.5, and FIG. 6, which is a top view of FIG. 5, show that the supportrollers (2a), (2'), and (2b), and the supplementary roller (15), aresupported by two parallel plates (3a) and (3b) which in their turn areconnected with slide (4). Said slide (4) is fastened with a series ofscrews to a base (10); while base (10) rotates about a vertical pin(11), and is sustained to frame (1) by means of bracket (12). Thepossible transversal rotation of base (10) and/or the whole trajectorysector (SS2) about said vertical pin (11) is in some cases utilized forthe purpose better described later on in FIG. 9.

In the case illustrated in FIGS. 5 to 9, the conductor (C) does not rundirectly on rollers (2a), (2') and (2b), but on an endless belt (14)which is tensioned by tension-roller (15) and set screw (16).

The number of rollers on one hand, and the strength of the endless belt(14) on the other hand have been studied to ensure the right support forconductor (C) and the right distribution of loads, or in other words, toavoid a wrong concentration of loads to damage the conductor and/or thebelt and/or the rollers.

Rollers (2a), (2b), and (15) rotate about pins (17) and can be easilydismounted by first unscrewing stop-nuts (18). The other rollers (2')(see FIG. 8, section VIII--VIII of FIG. 5) are instead mounted onbearings (19) fitted in special slots of plates (3a) and (3b).

Base (10) of plates (3a) and (3b) is also fitted with two additionalrollers (20). The cone-shaped end (20a) of said additional rollers (20)eases the positioning of conductor (C) in the space between said rollers(20). These additional rollers (20), having vertical axis, constitute alateral guide for the conductor (C) for the purpose better describedlater on.

The practical use and some of the operational advantages of the deviceillustrated in FIGS. 1 to 8, according to the present invention, aredescribed in the following points a) and b), and points (I) to (III).

a) While stringing suspending cables and/or conductors on a series oftowers, the new device is more or less used as a common pulley. Theframe (1) though is: 1) connected and anchored to the lower end of theinsulators in such a way (described for example in FIG. 12 and 13) as tonot occupy the points of attachment of the conductor and/or conductorsto the insulators, and 2) is supporting at least two trajectory sectors(SS1) and (SS2) and/or (SS3) and (SS4) rather than one or more pulleysheaves. The conductor and/or conductors therefore run either on saidroller (R) and (R') or on said belt (14) more or less in the same way ason a common pulley sheave. In fact, rollers (2a), (2'), and (2b), or (R)describe a circular and/or elliptic guiding surface which can ensurethat the conductors will not undergo and incompatible bending, due totheir own weight, once suspended from the towers and supported by saidsemi-sectors.

On the other hand, even though the conductor and/or conductors canfreely run on the new suspension device under the same conditions ofcommonly used pulley, the dimensions of the new suspension device areconsiderably smaller than said commonly used pulleys, and the weight hasconsiderably been reduced. This can easily be seen and understood bylooking at FIG. 3 where the dotted line (K) proportionally reproducesthe dimensions of a commonly used pulley sheave without its respectivelylarge supporting frame.

b) Once the conductor and/or conductors have been suspended from thetowers, said conductor and/or conductors have to be clamped-in to theinsulators. At this point, other essential and very important advantagesof the present invention become clear. In fact, the suspension unitcomprising a frame (1) and at least one pair of trajectory sectors (SS1)and (SS2) and/or (SS3) and (SS4) allows to invert the order andextremely simplify--both in terms of crews' work and the otherwiserequired supplementary equipment--the clamping-in operations, whileimproving crews' safety and the accuracy of the operations. Theoperations, already in the new order according to the present invention,are the following:

I. the conductors are first automatically positioned according to theprescribed geometric configuration (if required, that is to say in thecase of a bundle of more than one conductor), and then permanentlyclamped-in to the insulators while still being safely supported by saidtrajectory sectors. This is done by inserting the required suspensionclamps ((M) see for example FIG. 12) in the free central space betweensaid trajectory sectors (SS1) and (SS2) and/or (SS3) and (SS4), andanchoring said clamps to the plate hanging for the lower end of saidinsulators (see for example plate (33) FIG. 13).

II. Once the conductors have been clamped-in, said trajectory sectors(SS1) and (SS2) and/or (SS3) and (SS4) are lowered (as for exampleillustrated in FIGS. 1 to 3, position (3")) by hand and/or automatically(by means of at least one electric geared motor) operating on leadscrews (5), or (5a), or (9), in order to unload said trajectory sectorsof the weight of said conductors.

III. Once the trajectory sectors have been lowered, the frame, togetherwith said trajectory sectors, can easily and safely be disconnected fromthe insulators, and transfered either on the ground or suspended from another crossarm.

The clamping-in operations can therefore be carried out rapidly, withsimple interventions of the crews, and without the need to otherwise:lift the conductors by means of supplementary and temporary tackles,remove the pulleys leaving the conductors temporarily suspended from theground by means of said supplementary tackles, and finally clamp-in.

FIG. 9 illustrates a top view of a pair of trajectory sectors (SS1) and(SS2) which have been fitted with additional devices for betterstringing when transversal angles are present. That is to say whenconductor (C) meets trajectory sector (SS1) coming from the directionindicated with arrow (F), and departs from trajectory sector (SS2)according to the direction indicated with arrow (F'), or in other words,when the conductor and/or conductors have to undertake transversalangles equal to 1/2 AD+1/2 AD'.

In these cases, each trajectory sector (SS1) and/or (SS2) rotatetransversally about said vertical pin (11) (see also FIGS. 5 to 8) by asmany degrees as required and/or equal to 1/2AD and 1/2AD'. In order tosecure the right degree of transversal rotation of each trajectorysector before the conductor (C) is positioned on said trajectorysectors, setscrews (21) and/or one or more adjusting-springs can bebrought into contrast with frame (1). These setscrews (21) and or thementioned lead screws (5) can also be connected with at least oneremote-controlled geared motor.

When the deviation angle between directions (F) and (F') (equal to1/2AD+1/2AD') is relatively small, the four lateral rollers (20) will beenough to guide the conductor in the right direction. On the other hand,when said deviation angle is relatively large, one and/or two additionalseries of rollers (22), having vertical axis and being positionedaccording to a pre-calculated arc, can be inserted in the central spacebetween said two trajectory sectors (SS1) and (SS2) as illustrated inFIG. 9. Plates (23), which support said additional series of rollers(22), can also be adjusted for different angles by means of setscrews(23a) and/or adjusting-springs.

According to an other important characteristic of the present inventionthe rollers (2) and/or (2') of at least one of the two trajectory (SS1)and/or (SS2) could be connected, for example by means of tension roller(15), to a geared motor for the purpose better described later on. FIGS.10 and 11 illustrate an other possible way of motorization of rollers(2m) (similar to roller (2) and/or (2')) or a trajectory sector (SS5).These figures shown that some of said rollers (2m) have been connectedthrough their respective pins (24) (which extend beyond plate (3a)),gear (24a), chain (25), and pinion (26a), to a geared-motor (26). Theendless belt (14) has been eliminated, and rollers (2m), which have beencalendar=coated directly support the conductor (C). Both solutions, toeither calendar-coat said rollers with suitable materials, or to coverthem with said endless belt, have two functions: 1) to equallydistribute the weight of the conductor on each roller, and 2) to avoiddamaging the surface of the conductor and/or said rollers.

According to an other important characteristic of the present invention,the illustrated geared motor/s (26), for the automatic plumbing of theinsulators and the automatic sagging of the conductors, and/or the othergeared motors (not illustrated) for the automatic regulation of saidlead screws, are preferably constituted by low voltage electric-motors,for example 24 Volt. This characteristic implies that said motors caneither be fed by means of at least one battery, mounted on each frame(1), or by means of a single generator positioned on the ground anywhere between the brake and the winch. In this last case, that is to saywhen said electric motors are fed by means of a generator, in order toactivate said geared motors it is enough to connect the negative pole ofsaid low voltage to one tower (ground) and/or to one phase of the powerline, and the positive pole to each conductor and/or cable of each phaseof the power line, and/or to the conductors of at least one phase of thepower line. This enables to save all the batteries, otherwise to bemounted on each frame, to feed at once all electric motors mounted onall suspension devices between the brake and the winch, and consequentlyto plumb all insulators and sag all conductors at once withoutgenerating any danger of the crews. In fact: 1) 95% of the times therewill not be any need for any worker to be on any tower and/or to be incontact with any conductor, that is to say, 95% of the times all workerswill be waiting on the ground for the operation to be completed, and 2)even though in very few cases some workers might be on some towers, thevoltage will be so low (24 Volts and/or lower) that will be practicallyimperceptible at all effects.

Going back to FIGS. 10 and 11 again, said geared motor (26) can bemounted on a plate (27) which in its turn can rotate about pin (27a).Plate (27) is also fitted with a slot (27b) in order to be able toadjust set-screw (28). This particular way, already well known, ofconnecting said motor to supporting plates (3a) and/or (3b) allows tomove said motor and therefore properly tension said chain (25).

The mentioned electric motors are usually not fed during the stringingof the conductors and/or bundles of conductors on the series ofsuspension devices suspended from all towers between the brake and thewinch, but after all positioning and pre-sagging operations have beencompleted. As mentioned earlier, when a power line crosses mountainsand/or hills the commonly used pulley units, the strings of insulators,and the conductors become subject to loads which are not perfectlyvertical, or in other words, to longitudinal unbalances. Whilestringing, the pulley units and the insulators will therefore bedisplaced out-of-plumb, and even though the conductors will be pulled tothe right degree of tension (pre-sagging), the spans of said conductorsbetween one tower and the other will not describe the right sagging, orin other words the conductors will not be perfectly sagged. In thesecases it is necessary to bring the insulators back to a perfect plumbbefore the conductors can be clamp-in, or in other words the conductorshave to be lifted and pulled (sagged) to correct and undo saidlongitudinal unbalances.

In view of the just mentioned problem, the present invention revealsanother very important characteristic. In presence of longitudinalunbalances, once the positioning and pre-sagging of the conductors hasbeen completed, the electric motors (for example motors (26)) are fed.At this point, the motors act on said rollers (2) or (2m) and/or endlessbelt (14) and/or jaws (G1) (G2) (FIG. 4), and cause all conductorsand/or bundles of conductors and all strings of insulators to slide forvarious centimeters and/or meters so that: 1) said insulators will beautomatically plumbed, and 2) the conductor and/or conductors will beautomatically and perfectly sagged. The rotatory motion of the motorswill obviously always be in the right direction so as to allow saidautomatic plumbing, and/or the return of the insulators to a perfectlyvertical position.

Thanks to special verticality sensors mounted on each frame (shownschematically as sm), all the above mentioned automatic operations canbe controlled by one worker (on the ground), and/or by one worker on atower. It is to be understood that said sensors could also be associatedwith a central-control system cm.

When the geared motors are associated to said rollers and/or saidendless belt (see FIG. 10), a right degree of friction between theconductors and said rollers and/or belt is required in order to bringall insulators back to verticality. When the weight of each conductor oneach pair of trajectory sectors is not enough to ensure said rightdegree of friction, some counter-rollers (not illustrated) have to beapplied on top of each conductor in order to generate said right degreeof friction.

The need for the mentioned counter-rollers can be completely eliminatedthrough the preferred use of jaws (G1) and (G2) mounted in the centralspace between the two trajectory sectors (SS3) and (SS4) described inFIG. 4. Thanks to said geared-motors (MR1) and/or (MR2), and suitableverticality sensors, (not illustrated), said jaws (G1) and (G2) will,one at the time and/or one after the other, tighten the conductor, graspit, and pull it with repeated operations until the right sagging of saidconductor will be achieved and consequently till said insulators will beperfectly plumbed. It is to be understood that the intermittent workingof said jaws allows one pair of jaws (G1) to tighten and pull theconductor while the other jaws (G2) are in reverse motion; once the idlereverse motion of jaws (G2) has been completed, jaws (G2) will tightenthe conductor before jaws (G1) release it to perform their own idlereverse motion. Once said verticality sensors generate pulses toindicate that said verticality has been achieved, both jaws (G1) and(G2) will simultaneously grasp and lock the conductor now perfectlysagged.

FIGS. 12 and 13 show one possible alternative of a frame (1) fitted tosupport a bundle (for example) of three conductors (C1), (C2), and (C3).With this type of frame the three conductors will automaticallyundertake their final position, corresponding to the prescribed finalgeometric configuration (equilateral triangle), while been strung and/orpositioned on the series of suspension units. In fact, this frame hasbeen fitted: 1) with a pair of trajectory sectors per each conductor,each trajectory sector being of the same kind illustrated in FIGS. 1 and5, and 2) with an additional central slide (SC) for supporting the drawcable (T). When draw cable (T), connected to said three conductors, ispulled by the winch, each conductor of said bundle will be positioned onits respective couple of trajectory sectors. Conductors (C1) and (C2)will be directly positioned on their respective coupled of trajectorysectors (SSa) and (SSb), and conductor (C3) will automatically slidethrough guide (G) and reach trajectory sectors (SSc).

As illustrated in FIG. 1 and 5, each trajectory sector is mounted on theframe by means of a slide (4), so that once all conductors have beenclamped-in, by inserting one clamp (M) in the central space between eachcouple of trajectory sectors (only one clamp has been illustrated), alltrajectory sectors can be unloaded of the weight of the conductors, andthe whole suspension device can be brought back to the ground. FIG. 13also shows that conductors (C1) and (C2) can be directly clamped-in toplate (33) in correspodence of clamp-in points (AM1) and (AM2), while inorder to clamp-in conductor (C3), slide (SC), has to be first removed.It is to be understood that while slide (SC) can be easily removedbecause free of any loads (draw cable (T) is not resting on said slideonce the conductors are all in place), all clamp-in points (AM1), (AM2),(and (AM3) not illustrated), of plate (33) are also perfectly free, thatis to say that frame (1) and consequently all couples of trajectorysectors (SSa), (SSb), and (SSc) do not have to be removed before theclamp-in operation has been completed. As a matter of fact, plate (34),connected to plates (30A) and (30B) of said frame (1), overlaps plate(33) from the top consequently leaving the lower end of said plate (33)and the clamp-in points completely free. It is obvious that if necessaryat least one trajectory sector of each pair of trajectory sectors--(SSa)(SSb) and (SSc)--can be fitted with at least one geared/electric motor(as for example illustrated in FIG. 10) for the automatic plumbing ofthe insulators and the automatic sagging of the conductors.

FIGS. 14 and 15 show an additional alternative for frame (1). In thiscase the frame has been adjusted to be suspended from the insulators ofangle towers, and each pair of trajectory sectors has been fitted asillustrated in FIG. 9. This frame and each of these couples oftrajectory sectors have therefore been fitted to support: 1) the load ofthe conductors, and 2) the resultant force (indicated with arrow (P)) ofthe deviation angle (see FIG. 9) of said conductors.

FIGS. 16 to 19 show some details of the preferred disposition and shapeof rollers (R1), (R2), and (R3) of a trajectory sector (SS3) (and/or(SS4)) (see also FIG. 4). This alternative is the preferred one becauseit allows to use the same trajectory sectors for either line and/orangle towers, without the need of inserting and/or removing anyadditional devices.

Rollers (R1), (R2), and (R3) have different longitudinal dimensions,profiles, and supporting surface from one an other. The specialconfiguration of said rollers allows the conductor to: 1) run in thedirection indicated by arrows (F4) and (F3) (FIG. 16), and/or 2) runthrough any transversal direction angles starting from a minimum of forexample 1 degree of deviation up to angles equal to twice 1/2AD. Whenthe axis of rotation of said rollers are perfectly perpendicular toplates (L), the maximum deviation angle that said trajectory sectors(SS3) and (SS4) (which are for example 200 mm. wide) can sustain, whenfor example a 30 mm. diameter conductor is passing through, isapproximately equal to 60 degrees.

FIG. 17 shows the the couple of plates (L) that support the rollers arefitted with more series of through-holes (40), (41), and (42). Theseseries of through-holes are used to tilt pins (43), (44), and (45) inorder to change the inclination the axis of rotation of said rollers(R1), (R2), and (R3). FIG. 18 is a front view of said trajectory sector(SS3) where the axis of rotation (A1), (A2), and (A3) of said rollersare perfectly perpendicular to plates (L). This is the case where themaximum transversal angle of deviation allowed to the conductor (C) isapproximately equal to 60 degrees. By tilting said axis (see FIG. 19)either according to positions (A1'), (A2'), and (A3') or positions(A1"), (A2"), and (A3"), that is to say by mounting said pins (43),(44), and (45) in corresppondence of through-holes (40) (41) on oneplate (L) and (41) (42) on the other plate (L), the maximum transversalangle of deviation allowed to a conductor (C) (when the diameter of saidconductor is equal to 30 mm. and the distance between plates (L) isequal to 200 mm.) becomes approximately equal to 80 degrees. Saidtilting of said axis of rotation also grants stability to oscillationseven in windy conditions to conductors and/or any other type of cableused.

FIGS. 16 and 18 also show the special concave profile of each roller. Infact, while rollers (R1) and (R2) have profiles (R1') and (R2") similarto an elliptic hyperboloid, the profile of roller (R3) is actuallyformed by two different geometric shapes: (R3') similar to an elliptichyperboloid, and (R3") similar to a hyperbolic hyperboloid. Thedevelopment of the different concave profiles of each roller (R1), (R2),and (R3) (see FIG. 16 and 18) allows: 1) to be able to string conductorswith different diameters using the same rollers (the maximum transversalangle of deviation allowed to each of said conductors will obviouslychange according to the size of the conductors and/or the distancebetween the two plates (L)), and 2) to ensure that said conductors canbe pulled through transversal angles of deviation without neitherdamaging the conductors nor the rollers.

Thanks to the special longitudinal sizes and profiles of said rollers(R1), (R2), and (R3) and the possibility of changing the inclination ofthe axis of rotation of said rollers, the sectors do not have to bemounted on said vertical pins (11) (FIG. 5) any more, and saidadditional rollers (22) (FIG. 9) do not need to be inserted in thecentral space between each pair of sectors any more either.

FIG. 20 finally illustrates the preferred type of frame. This frame hasa reticular structure which allows to further decrease the overallweight of the whole suspension device. It is constituted with rodsrather than plates each rod being preferably made with alloy and/orother material channel sections. This figure shows that the reticularbase (51) of this frame can support one, two, and/or three jacks (52),(53), and (54). Each jack supports a pair of trajectory sectors (55),(56), and (57) of the same type illustrate in FIGS. 4 and 16 to 19. Whenusing this type of frame, the conductors (not illustrated) are strungand positioned on their respective pairs of trajectory sectors when saidtrajectory sectors are laying on the same horizontal plane. Jacks (52),(53), and (54), allow: 1) to tilt, if necessary, the pairs of trajectorysectors (as compared to the horizontal plane of base (51) and thelongitudinal axis of the conductors), in order to decrease the influenceof longitudinal unbalances on the insulators and the conductors, 2) oncethe conductors have been strung and pre-sagged, to position saidconductors according to the prescribed geometric configuration (forexample position (55') and (57') of trajectory sectors (55) and (57)),and 3) once the conductors have been perfectly sagged and the insulatorsperfectly plumbed (thanks for example to jaws (G1) and (G2) illustratedFIG. 4), and once the conductors have been clamped-in, to unload theweight of each conductor from each pair of trajectory sectors and thenremove the whole suspenstion device.

The functions of jacks (52), (53), and (54) can all be accomplished byhand-operating set-screws (58), (59), and (60) or by acting on saidscrews by means of one or more remote-controlled electric motors.

The frame described in this figure also comprises a series of verticalrods (60) and (61), and a plurality of cross members (62) (63) whichconverge towards interface (64). Interface (64), which is required toanchor the whole suspension device to the insulators, is fitted with oneor more grooves (not shown) to overlap to plate (33) (plate illustratedin FIG. 13). By integrating said interface (64) with some check-pins(not illustrated), the anchoring systems will have a tensile strengtheven greater than the tensile strength of the insulators themselves. Itis to be understood that this anchoring system also prevents anyrelative movement between said plate (33) and said suspension frame.

This reticular frame illustrated in FIG. 20, has on overall "C" shape(open on one side) as it was the case for the frames illustrated inFIGS. 12 to 15, but on the other hand, even though it might seem to bemore fragile than the other ones it is actually much stronger, has awider side opening, and it weighs less.

Finally, it is also to be noticed that this reticular frame can be veryeasily adapted to support any number of jacks and/or pairs of trajectorysectors for any number of conductors in a bundle to be positionedaccording to any geometric configuration.

I claim:
 1. Suspension device for the stringing of electric conductors(C) for overhead power lines, comprising: a suspension frame (1) adaptedto be anchored to a crossarm of a tower of the line, and means for thesupport and sliding of the conductors (C), said support and slidingmeans comprising, for each conductor, a plurality of support rollers (2,2') rotating about parallel pins, said rollers being aligned one afterthe other along a curved trajectory defining a support and slidingsurface for the conductor, said support rollers (2, 2') for eachconductor being divided in two groups forming a pair of trajectorysectors (SS1, SS2), said sectors (SS1, SS2) of each pair supporting eachconductor (C) being mounted on the suspension frame (1) in specularsymmetry with respect to a central vertical suspension axis of saidframe, said two sectors of each pair being mounted on a common supportcrossmember (P1) and being mutually spaced, said device furtherincluding lifting and lowering means (5, 5a, 8, 8', 8", 9) liked to saidsectors, for moving the sectors in a substantially vertical direction,said lifting and lowering means acting on said common supportcrossmember (P1).
 2. Device as in claim 1, wherein the suspension framecomprises a free central space along its vertical suspension axis, andthe two sectors are symmetrically positioned on both sides of saidcentral space.
 3. Device as in claim 2, wherein said free central spacehas a transversal dimension exceeding the length of an anchor andsuspension clamp (M) for the conductor (C).
 4. Device as in claim 2,wherein said free central space has a transversal dimension exceedingthe length of an anchor and suspension clamp (M) plus the respectivefittings.
 5. Device as in claim 1, wherein said lifting and loweringmeans move each pair of sectors from a lifted working position, in whichthe rollers (2, 2') support the load of the conductor (C), to a loweredrest position, in which said rollers are unloaded of the weight of theconductor.
 6. Device as in claim 5, wherein said common supportcrossmember (P1) is mounted on the suspension frame by means of apantograph support (8, 8'), and said lifting and lowering means (9)control the opening of the pantograph.
 7. Device as in claim 6, whereinsaid pantograph support comprises a double pantograph (8, 8', 8") andsaid crossmember supporting the pair of sectors is movable verticallyand/or in a direction slightly oblique with respect to the verticaldirection.
 8. Device as in claim 5, wherein said lifting and loweringmeans consist of adjusting screws (5).
 9. Device as in claim 8, furtherincluding driving means for operating said adjusting screws.
 10. Deviceas in claim 9, wherein said driving means comprise electric motors fedwith low voltage.
 11. Device as in claim 10, further including electricinsulation means interposed between the conductors and said motors, saidlow voltage being fed through said conductors.
 12. Device as in claim 1,comprising means for shifting (26, 2, 2m, 14, 25, G1, G2) the conductorwith respect to the pair of sectors supporting the same.
 13. Device asin claim 12, wherein said shifting means comprise motor means (26)associated to at least one of the support rollers (2, 2m) of each sectorand adapted to cause its rotation in either of the two slidingdirections of the conductor.
 14. Device as in claim 13, wherein saidshifting means comprise at least one supplementary wheel, driven bymotor means and associated to each trajectory sector, said wheel beingapplied by pressure onto the conductor.
 15. Device as in claim 12,wherein said shifting means comprise two opposed driving wheels, whichclamp the conductor on diametrically opposite sides and which are drivenby common motor means.
 16. Device as in claim 12, wherein said shiftingmeans comprise at least one pair of jaws (G1, G2) for clamping theconductor, each jaw being mounted on a respective slide sliding parallelto the conductor, and motor means (MR1, MR2) associated to each of saidslides for controlling their forward movement with the jaw clamping theconductor and, respectively, their backward movement with an open jaw.17. Device as in claim 16, wherein the forward movement of one of theclamping jaws is controlled simultaneously with the backward movement ofthe other jaw, said forward movement taking place in either of the twosliding directions of the conductor.
 18. Device as in claim 17, whereinsaid clamping jaws are housed in a free central area of the suspensionframe, between each pair of sectors.
 19. Device as in claim 12, furthercomprising verticality sensors associated to said suspension frame forgenerating signals.
 20. Device as in claim 19, further comprisingautomatic control means associated to each suspension frame foroperating said conductor shifting means in response to signals generatedfrom said sensors.
 21. Device as in claim 20, wherein said automaticcontrol means include means to lock the conductor with respect to thesuspension frame.
 22. Device as in claim 1, wherein the bearing surfacesof the support rollers of each trajectory sector have a concave profile.23. Device as in claim 22, wherein said concave bearing surface hasraised end edges.
 24. Device as in claim 22, wherein said concavebearing surface has a double-groove profile (R3', R3").
 25. Device as inclaim 22, wherein the concave profile (R1') of said bearing surface ofthe support rollers comprises an arched central portion with widecurvature radius and arched end portions with a small curvature radius.26. Device as in claim 26, wherein said support rollers have a profilesimilar to an elliptical hyperboloid.
 27. Device as in claim 26, whereinsaid support rollers have a profile partly similar to an ellipticalhyperboloid and partly similar to an hyperbolic hyperboloid.
 28. Deviceas in claim 22, wherein the support rollers of one sector have differentlengths, the smallest roller (R3) being the one closer to the centralsuspension axis.
 29. Device as in claim 22, wherein the support rollersof one sector have different radiuses, the roller with the smallestradius being the one (R3) closer to the central suspension axis. 30.Device as in claim 1, wherein the support rollers of each of saidsectors are mounted rotating about pins carried by a support bracketconsisting of a pair of stiffly interconnected and mutually spacedplates (L).
 31. Device as in claim 30, wherein said plates (L) of eachsupport bracket are parallel and said support rollers all have the samelength.
 32. Device as in claim 30, wherein said plates of each supportbracket are divergent and said rollers have progressively increasinglengths, starting from the central suspension axis.
 33. Device as inclaim 30, wherein each of the support rollers is mounted rotating abouta pin, which is anchored in a fixed position to said pair of plates. 34.Device as in claim 30, wherein each of the support rollers is mountedrotating about a pin, the position of which is adjustable with respectto said pair of plates.
 35. Device as in claim 34, wherein the pin ofeach of the support rollers is mounted with its ends on twosupplementary support plates, each of which is adapted to be anchored inan adjusted position onto one of the plates forming said supportbracket.
 36. Device as in claim 34, further including means for settingeach of the pins (43, 44, 45) of said support rollers in an inclinedposition.
 37. Device as in claim 36, wherein each of the plates of saidpair has a plurality of seats (40, 41, 42) for housing the ends of eachof the pins (43, 44, 45) of said support rollers.